1. Background of the Invention
This invention relates to improvements in oil well pumping apparatus and more particularly to improvements in standing valves of the type commonly employed at the bottom of an oil well for allowing production fluid to pass freely upwardly and for closing against undesirable backflow.
2. Description of the Prior Art
In oil wells, a string of tubing extends downwardly to the well casing and oil is pumped out of the well through the tubing by means of a pump located adjacent the bottom of the well. The pump normally includes a foot or check valve or other equivalent valve means to prevent unintentional flow of liquid downwardly through the tubing so that in the event that the pump is stopped for any reason, the fluid head of liquid in the tubing will not be lost. Frequently, however, it is desired for various reasons to interrupt the production of a well in order to remove the pump and the entire string of tubing from the well. In such circumstances, unless the head of liquid can first be drained or otherwise removed from the tubing, it becomes necessary to remove the tubing while the latter is filled with liquid. For this reason, it is accepted practice to provide a means of draining the tubing with tools run into the well on a wire line, or otherwise opening ports to drain the fluid from the tubing back into the well bore. The standing valve may then be retrived with the wire line without the added load of unseating against the head of liquid in the tubing. The load of an upstanding column of production fluid, which may be of considerable weight and height above the valve, causes undue strain on and breakage of any of the wire line, the clutching connection, the valve unit, and the production string.
The prior art has long been concerned with improvements in oil well standing valves. Exemplary of the patents in this area include U.S. Pat. Nos. 2,854,929, in the name of Harold E. McGowen, Jr., et al.; 2,752,861, in the name of Robert H. Hill; 1,956,112, in the name of Wayne W. Willoughby; and 1,644,998, in the name of Robert W. Gunn, et al. However, prior art standing valves have been unsuccessful because they do not allow the maximum possible fluid flow from the well and also still allow the valve to be easily drained and retrieved through the tubing.
Furthermore, standing valves commonly use flow of all produced fluids around a poppet or ball, but within the standing valve body, greatly reducing the flow area of the seat. Such structure does not allow for maximum possible fluid flow.